Description:

This instruction performs a compare between register Rd and a constant. The register is not changed. All conditional branches can be used after this instruction.

Operation:

Rd - K

Syntax: Operands: Program Counter:

CPI Rd,K 16 ≤ d ≤ 31, 0≤ K ≤ 255 PC ← PC + 1

16-bit Opcode:

0011

KKKK

dddd

KKKK

Status Register (SREG) and Boolean Formula:

I

T

H

S

V

N

Z

C

-

-

H:

Set if there was a borrow from bit 3; cleared otherwise

S: N ⊕ V, For signed tests.

V:

Set if two's complement overflow resulted from the operation; cleared otherwise.

N:R7 Set if MSB of the result is set; cleared otherwise.

Z:

Set if the result is $00; cleared otherwise.

C:

Set if the absolute value of K is larger than the absolute value of Rd; cleared otherwise.

R (Result) after the operation.

Example:

cpi r19,3 ; Compare r19 with 3
brne error ; Branch if r19⇔3
...
error: nop ; Branch destination (do nothing)

Words: 1 (2 bytes)

Cycles: 1